Exposure method and exposure apparatus

ABSTRACT

In a method executed in an exposure apparatus, a focus control effective region and a focus control exclusion region are set based on an exposure map and a chip area layout within an exposure area. Focus-leveling data are measured over a wafer. A photo resist layer on the wafer is exposed with an exposure light. When a chip area of a plurality of chip areas of the exposure area is located within an effective region of a wafer, the chip area is included in the focus control effective region, and when a part of or all of a chip area of the plurality of chip areas is located on or outside a periphery of the effective region of the wafer, the chip area is included in the focus control exclusion region In the exposing, a focus-leveling is controlled by using the focus-leveling data measured at the focus control effective region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 15/906,580,filed Feb. 27, 2018, now U.S. Pat. No. 10,747,128, which claims priorityto U.S. Provisional Patent Application 62/586,641, filed Nov. 15, 2017,the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to a patterning method and an apparatus forfabricating resist patterns in device manufacturing, such as anintegrated circuit, more particularly to a lithography process andlithography apparatus, such as a scanner and a stepper.

BACKGROUND

As the semiconductor industry introduces new generations of integratedcircuits (ICs) having higher performance and greater functionality, thedensity of the elements that form the ICs is increased, while thedimensions and spacing between components or elements of the ICs arereduced. As components become smaller and patterning techniques becomemore precise, a precise focus and/or leveling control during theexposure operation has been required.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 shows a schematic view of an exposure apparatus related toembodiments of the present disclosure.

FIG. 2 shows a schematic view of a focus-leveling measurement systemrelated to embodiments of the present disclosure.

FIGS. 3A, 3B and 3C show a concept of measuring and controllingfocus-leveling related to embodiments of the present disclosure.

FIG. 4 shows a concept of measuring and controlling focus-levelingrelated to embodiments of the present disclosure.

FIGS. 5A and 5B show a concept of measuring and controllingfocus-leveling related to embodiments of the present disclosure.

FIGS. 6A and 6B show a concept of measuring and controllingfocus-leveling according to embodiments of the present disclosure.

FIG. 7 shows a flow chart of an exposure operation according toembodiments of the present disclosure.

FIGS. 8A and 8B show various exposure maps related to embodiments of thepresent disclosure.

FIGS. 9A, 9B, 9C, 9D, 9E, 9F and 9G show various chip area layoutrelated to embodiments of the present disclosure.

FIGS. 10A and 10B show defocus-risk chip areas related to embodiments ofthe present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

In the step-and-scan exposure system, the region where the patterns onthe photo mask is projected on to the wafer by one scan (i.e., anexposure area or an exposure field) is limited, and the exposing scan isrepeated by driving the wafer stage to move the wafer sequentiallyaccording to an exposure map on the wafer. In such an exposure system ahighly precise focus control is required.

FIG. 1 shows an exemplary exposure apparatus related to embodiments ofthe present disclosure. The exposure apparatus 100 is a projectionoptical exposure apparatus, for example, an optical scanner or anoptical stepper used for a lithography process in a fabrication of asemiconductor device or a flat panel display. Further, the exposureapparatus 100 can be a local liquid immersion exposure apparatus thatperforms exposure in a state where a space between a lower surface of anoptical system and a wafer surface is locally filled with a liquid.

The exposure apparatus 100 includes, among other features, a lightsource 15, for example, a KrF excimer laser system or an ArF excimerlaser system, one or more mirrors 20, a condenser lens 25, a photo maskstage 32 that holds a photo mask (reticle) 30, a wafer stage 45, aprojection lens system 35, a wafer alignment measurement system 55, afocus-leveling measurement and control system 50, and a controller 60.The controller 60 includes one or more processing circuits, such as aCPU or a microprocessor, and one or more storage devices (memory) 65,such as a hard disk drive or a flash memory. The controller 60, byexecuting one or more control programs stored in the storage device 65by the processing circuit, controls operations of the exposure apparatus100 according to the control program.

As shown in FIG. 1, the Z direction is parallel an optical axis AX of aprojection lens system 35, the Y direction is the direction in which aphoto mask 30 and a wafer 40 are relatively scanned, and the X directionis the direction orthogonal to the Z direction and the Y direction.

When the exposure apparatus 100 is an optical scanner, a slit-shapedillumination area which is set over the photo mask 30 with a reticleblind is illuminated by the illumination light (exposure light) emittedfrom the light source 15. The photo mask 30, on which a circuit patternis formed as transparent or opaque patterns, is held on the mask stage32. The mask stage 32 can be precisely driven within the XY plane, andcan also be moved in the predetermined scanning direction (Y direction),by mask stage driving mechanism 34. The projection lens system 35projects illumination light passing through the photo mask 30 on to thewafer 40 placed on a wafer stage 45. By synchronous driving of the maskstage 32 and the wafer stage 45, which relatively moves the mask stage32 in the scanning direction (+Y direction) and moves the wafer stage 45on which the wafer 40 to be exposed is placed, in opposing the scanningdirection (−Y direction). By this scanning movement, a band ofillumination light is scanned in an exposure area on the wafer to form amask pattern image on/in a photo resist layer coated on the wafer 40.

FIG. 2 shows a schematic configuration of a focus-leveling measurementand control system 50 of the exposure system 100.

The focus-leveling measurement and control system 50 includes anautofocus control system 210 and a leveling measuring system 220. Insome embodiments of the present disclosure, a focus measurement measuresa height of the surface of the wafer, and a leveling measurementmeasures a tilt of the exposure area. Further, a focus-levelingcontrol/measurement means controls or measures both the focus (height)and the leveling (tilt).

The leveling measuring system 220 includes a light source 222 foremitting, e.g., broadband light, a multi slit unit 224, a first opticalsystem 226, and a second optical system (light receiving part) 228. Thesecond optical system 228 performs photoelectric conversion of the inputlight spots and outputs the information on two-dimensional lightintensity.

The autofocus control system 210 receives information on two-dimensionallight intensity from the second optical system 228. By using theinformation on two-dimensional light intensity, the autofocus controlsystem calculates a height of the surface of the exposure area (photoresist layer) and a tilt of the exposure area, and then calculates adirection of the controlled variable of the wafer stage 45, anadjustment amount of the Z direction of the wafer stage 45, and/or adirection and an amount of inclination adjustment of the wafer stage 45.The wafer stage 45 is controlled accordingly during the exposure(scanning). To determine the plane of the surface of the exposure area,at least 3 measuring points (light spots) are necessary. In someembodiments, 6-12 points are measured to determine the tilt of theexposure area.

In the exposure operation, a wafer 40, such as a semiconductor wafer ora glass plate for a flat panel display, is loaded on the wafer stage 45.Unless the wafer 40 has no underlying pattern, the wafer alignmentmeasurement system 55 detects, by using a laser beam, alignment patternsformed by the underlying patterns. For example, the wafer 40 has aplurality of exposure areas arranged in the X direction and the Ydirection as a matrix, and each exposure area includes one or more areascorresponding to a semiconductor chip. The alignment patterns include analignment pattern for the X direction and an alignment pattern for the Ydirection, arranged in a scribe lane between chips in some embodiments.Based on the alignment measurement result, the wafer 40 (wafer stage 45)is moved to a predetermined position under the projection lens 35, andthe first exposure area in the wafer 40 is exposed with the laser light.Then, the wafer 40 is moved so that the next exposure area is exposed.Such moving and exposing are repeated until all of the exposure areas inthe wafer 40 are exposed. Before and during the exposure, the focusvalue (the stage height) and a leveling value (tilt of the stage) arecontrolled. Then, the exposed wafer 40 is unloaded and the next wafer isloaded to be exposed.

In some embodiments, the focus-leveling measurement is performed justbefore the exposure. FIGS. 3A-3C show a focus-leveling measurementoperation related to embodiments of the present disclosure. For thepurpose of explanation, it is assumed that one exposure area 300 isdivided into four exposure sub-areas. In FIGS. 3A-3C, the scanning isperformed along the Y direction. When the first area 310 is exposed(scanned), the leveling measurement for the second area 320 is performedby the measurement light beams 350. Then, the exposure for the secondarea 320 is performed with focus-leveling controlled by using theleveling measurement results for the second area 320. When the secondarea 320 is exposed (scanned), the leveling measurement for the thirdarea 330 is performed. Then, the exposure for the third area 330 isperformed with focus-leveling controlled by using the levelingmeasurement results for the third area 330. When the third area 330 isexposed (scanned), the leveling measurement for the fourth area 340 isperformed. In the actual exposure system, the scanning is performed in acontinuous manner and the focus-leveling measurements are also performedcontinuously or dynamically.

In FIGS. 3A-3C, the measurement light beams 350 (e.g., nine light beams)are all located in the exposure area in the X direction. However, whenthe exposure area in the X direction is smaller, one or more of themeasurement light beams 350 are not utilized.

In other embodiments, the focus-leveling measurement is performed forthe entire wafer and the measured results are stored in a memory. Inexposing a given exposure area, the pre-measured focus-leveling data isread out from the memory, and the exposure (scan) for the given exposurearea is performed with focus-leveling controlled.

When an exposure area is located sufficiently within inside the wafer,the exposure area is exposed with the exposure light while preciselycontrolling the focus and leveling by using the measured focus-levelingdata. However, for exposure areas located near the outer periphery ofthe wafer, a part of the exposure area is located at “a focus controlexclusion region” and the exposure areas located in the focus controlexclusion region may be exposed without precisely controlling the focusand leveling, because a part of the focus-leveling data is not used. Insuch a case, the exposed area without precisely controlling the focusand leveling is subjected to a defocus risk, and semiconductor chipscorresponding to such area would become “bad” chips.

FIG. 4 shows a concept of the focus control effective region and thefocus control exclusion region. In FIG. 4, the boundary 415 between thefocus control effective region 410 and the focus control exclusionregion 420 has a circular shape having the center thereof coincidingwith the center of the wafer 400. As shown in FIGS. 3A-3C and 4, thefocus-leveling measurement utilizes multiple light beams 330, forexample, nine light beams (spots) arranged in the X direction, as agroup of measurement light beams. Although FIG. 4 shows discrete lightbeams along the Y direction, the focus-leveling measurement light beams330 are scanned by moving the wafer stage relative to the wafer 400.

When the entire group of measurement light beams 330 (nine light beamsalong the X direction) is within the focus control effective region 410generating valid focus-leveling data, the focus-leveling control isperformed by using the valid focus-leveling data. In contrast, when apart of the group of measurement light beams 330 is located outside thefocus control effective region 410, i.e., in the focus control exclusionregion 420, the focus-leveling measurement data corresponding to thefocus control exclusion region 420 become invalid focus-leveling data417 and 419 in some embodiments. In other embodiments, thefocus-leveling measurement for the focus control exclusion region 420 isnot performed or measurement data for the focus control exclusion region420 are not stored. In some embodiments, when the part of the group ofmeasurement light beams is located in the focus control exclusion region420, all focus-leveling measurement data in the group become invalidfocus-leveling measurement data. The invalid focus-leveling measurementdata is not utilized in the focus-leveling control, and thus this maygenerate a defocus issue. As shown in FIG. 4, the invalid focus-levelingdata includes first invalid focus-leveling data 417 and second invalidfocus-leveling data 419. The first invalid focus-leveling data 417 arefor the focus control exclusion region 420 within the outer boundary ofthe wafer 400, and the second invalid focus-leveling data 419 are forthe region outside the outer boundary of the wafer 400.

In general, one exposure area 300 includes multiple chip areas havingsubstantially the same circuit patterns. For example, FIG. 5A shows thecase where one exposure area 501 includes 4×6 (24) chip areas 511, andFIG. 5B shows the case where one exposure area 502 includes 2×2 (four)chip areas 512. As set forth above, when the exposure area 501 or 502 islocated near the outer periphery (edge) of the wafer 400, thefocus-leveling control may not be sufficiently performed.

In the case of FIG. 5A, when the focus-leveling measurement points(light beam spots) corresponding to a given chip area is located in thefocus control exclusion region 420, the chip areas 533 may have a riskof insufficient focus-leveling control because the focus-levelingmeasurement data correspond to the given chip areas 533 are not used. Itis noted that when the measurement point is located out of the outerperiphery of the wafer 400, no measurement is performed for the chipareas 535.

In the case shown in FIG. 5A, for the exposure area 521, two chip areas,which are located in the focus control exclusion area 415 and wouldotherwise be good chips, may have a risk of insufficient focus control,and 22 chip areas are valid chip areas 531. More specifically, the chipareas corresponding to the matrix (3, 7) and (3, 8), where (x, y)corresponds to the row and column of the multiple chips within theexposure area, are invalid chip areas 533, and the focus-levelingmeasurement data corresponding to the invalid chip areas 533 are notused in the focus-leveling control during the exposure. Thus, these chipareas may be subjected to the risk of insufficient focus control, andthus are excluded from “good” chips.

For the exposure area 522, seven chip areas, which are located in thefocus control exclusion area 415 and would otherwise be good chips, mayhave a risk of insufficient focus control, and 17 chip areas are validchip areas 531. More specifically, the chip areas corresponding to thematrix (1, 5), (1, 6), (2, 4), (3, 3), (3, 4), (4, 2) and (4, 3) areinvalid chip areas 533, and the focus-leveling measurement datacorresponding to the invalid chip areas 533 are not used in thefocus-leveling control during the exposure. Thus, these chip areas maybe subjected to the risk of insufficient focus control, thus be excludedfrom “good” chips.

For the exposure area 523, six chip areas, which are located in thefocus control exclusion area 415 and would otherwise be good chips, mayhave a risk of insufficient focus control, and 18 chip areas are validchip areas 531. More specifically, the chip areas corresponding to thematrix (2, 6), (3, 4), (3, 5), (4, 1), (4, 2) and (4, 3) are invalidchip areas 533, and the focus-leveling measurement data corresponding tothe invalid chip areas 533 are not used in the focus-leveling controlduring the exposure. Thus, these chips areas may be subjected to therisk of insufficient focus control, and thus are excluded from the“good” chips.

In the exposure areas 521, 522 and 523, the chip areas located on oroutside of the outer periphery of the effective region of the wafer 400are considered as invalid chips and no focus-leveling data are measuredor, even if measured, the data is not used in the focus-levelingcontrol. In some embodiments, the effective region of the wafer 400 isset smaller than the physical periphery of the wafer 400. The effectiveregion of the wafer 400 is set in consideration of an edge cut amount inphoto resist coating and/or a mechanical clamping margin in a filmdeposition device or an etching device. In some embodiments, theeffective region of the wafer is set smaller by about 2 mm to about 15mm in diameter than the wafer. When the wafer 400 is 300 mm diameterwafer, the effective region of the wafer 400 (the diameter) is set in arange from 285 mm to 295 mm, in some embodiments. For simplicity, thepresent drawings show the edge of the wafer as the outer periphery ofthe effective region of the wafer 400.

The number of such risk-bearing chip areas depends on the matrixarrangement of the multiple chip areas in one exposure area.

In the case shown in FIG. 5B, 2×2 (four) chip areas 512 are included inone exposure area 502. For the exposure area 541, one chip area, whichis located in the focus control exclusion area 415 and would otherwisebe a good chip, may have a risk of insufficient focus control, one chiparea overlaps the outer periphery of the effective region of the wafer400, and only two chip areas are good chip areas 551 (with sufficientfocus-leveling control). More specifically, the chip area correspondingto the matrix (1, 2) is an invalid chip area 553, and the focus-levelingmeasurement data corresponding to the invalid chip area 553 are not usedin the focus-leveling control during the exposure. Thus, the chip areasmay be subjected to the risk of insufficient focus control, and thus areexcluded from the “good” chips.

For the exposure area 542, one chip area, which is located in the focuscontrol exclusion area 415 and would otherwise be a good chip, may havea risk of insufficient focus control, and no chip areas are a good chiparea 551 (with sufficient focus-leveling control). More specifically,the chip area corresponding to the matrix (1, 1) is an invalid chip area553, and the focus-leveling measurement data corresponding to theinvalid chip area 553 are not used in the focus-leveling control duringthe exposure. Thus, the chip areas may be subjected to the risk ofinsufficient focus control, and thus are excluded from the “good” chips.

Further, for the exposure area 543, one chip area, which is located inthe focus control exclusion area 415 and would otherwise be a good chip,may have a risk of insufficient focus control, and three chip areas aregood chip areas 551 (with sufficient focus-leveling control). Morespecifically, the chip area corresponding to the matrix (2, 2) is aninvalid chip area 553, and the focus-leveling measurement datacorresponding to the invalid chip area 553 are not used in thefocus-leveling control during the exposure. Thus, the chip areas may besubjected to the risk of insufficient focus control, and thus areexcluded from the “good” chips.

In the exposure areas 541, 542 and 543, the chip areas located on oroutside of the outer periphery of the effective region of the wafer 400are considered as invalid chips 553 and no focus-leveling data aremeasured or, even if measured, the data is not used in thefocus-leveling control. It is noted that when the measurement point islocated out of the outer periphery of the wafer 400, no measurement isperformed for the chip areas 555.

As set forth above, when a simple circular boundary between the focuscontrol effective region and the focus control exclusion region is set,many chip areas are subjected to insufficient focus-leveling control,and thus a yield of the chips would decrease.

According to one aspect of the present disclosure, the focus controlexclusion region is not fixed as a circular shape, but is flexibly setin accordance with an exposure map and a chip layout within the exposuremap.

As shown in FIGS. 6A and 6B, the boundary 615 or 617 between the focuscontrol effective region 610 and the focus control exclusion region 620is set along the chip area boundaries. In some embodiments, as long as achip area is located within the periphery of the effective region of thewafer 400, the chip area is classified as a valid chip area 531 or 551and is included in the focus control effective region 610. As set forthabove, the focus-leveling measurement data corresponding to the validchip areas 531 or 551 are used for the focus-leveling control during theexposure. When a part of or all of the chip area is located on oroutside of the outer periphery of the effective region of the wafer 400,the chip area is considered as an invalid chip area 535 or 555, and thearea corresponding to the invalid chip areas is set as the focus controlexclusion region 620.

In the case of FIG. 6A, compared with FIG. 5A, the exposure area 521does not include any invalid chip area. The chip areas corresponding tothe matrix (3, 6) and (3, 7) are located within the outer periphery ofthe effective region of the wafer 400, and thus valid chip areas 531.The focus-leveling measurement data corresponding to these valid chipareas 531 are used in the focus-leveling control during the exposure.Thus, the chip areas would likely be manufactured as “good” chips. Inother words, compared with a circular setting 515 of the focus controlexclusion region 520 as shown in FIG. 5A, two chips are saved as a goodchip.

Similarly, the exposure area 522 includes eight invalid chip areas 535(1, 6), (2, 5), (2, 6), (3, 5), (3, 6), (4, 4), (4, 5) and (4, 6), whichare located on or outside of the outer periphery of the effective regionof the wafer 400. The chip areas corresponding to the matrix (1, 5), (2,4), (3, 3), (3, 4), (4, 2) and (4, 3) are located within the outerperiphery of the effective region of the wafer 400, and are valid chipareas 531. The focus-leveling measurement data corresponding to thesevalid chip areas 531 are used in the focus-leveling control during theexposure. Thus, these chips areas would likely be manufactured as “good”chips. In other words, compared with a circular setting 515 of the focuscontrol exclusion region 520 as shown in FIG. 5A, six chips are saved asgood chips.

Further, the exposure area 523 includes four invalid chip areas 535 (3,6), (4, 4), (4, 5), and (4, 6), which are located on or outside of theouter periphery of the effective region of the wafer 400. The chip areascorresponding to the matrix (2, 6), (3, 4), (3, 5), (4, 1), (4, 2) and(4, 3) are located within the outer periphery of the wafer, and arevalid chip areas 531. The focus-leveling measurement data correspondingto these valid chip areas 531 are used in the focus-leveling controlduring the exposure. Thus, these chips areas would likely bemanufactured as “good” chips. In other words, compared with a circularsetting of the focus control exclusion region as shown in FIG. 5A, sixchips are saved as good chips.

Although FIG. 6A shows only a part of the boundary 615 between the focuscontrol effective region and the focus control exclusion region, theboundary is set for the entire exposure map over the wafer.

The same or similar effects can be obtained for the case of a 2×2 chipmatrix. As shown in FIG. 6B, for the exposure area 541, one chip areacan be saved as a valid chip area 551 compared with a circular settingof the focus control exclusion region as shown in FIG. 5B, for theexposure area 542, one chip area can be saved as a valid chip area 551compared with a circular setting of the focus control exclusion regionas shown in FIG. 5B, and for the exposure area 543, one chip area can besaved as a valid chip area 551 compared with a circular setting of thefocus control exclusion region as shown in FIG. 5B. The chip areaslocated on or outside of the outer periphery of the effective region ofthe wafer 400 remain invalid chip areas 555.

In the foregoing embodiments, the boundary 615 and/or 617 between thefocus control effective region 610 and the focus control exclusionregion 620 is not circular, and is not fixed. In some embodiments, theboundary 615 and/or 617 between the focus control effective region 610and the focus control exclusion region 620 has multiple corners. Themultiple corners include 90 degree corners and 270 degree corners. Inother words, the boundary between the focus control effective region andthe focus exclusion region is a zig-zag pattern.

Further, as shown in FIGS. 6A and 6B, different focus control effectiveregion 610 and focus control exclusion region 620 can be set fordifferent exposure maps and chip area layout in the exposure area.

FIG. 7 shows an operational flow of exposing wafer by using a opticalscanner according to an embodiment of the present disclosure. Theoperational flow of FIG. 7 can be realized by a program or softwareexecuted by a processor (computer). In some embodiments, anon-transitory computer readable medium (e.g., 65 shown in FIG. 1)stores a program, and when the program is executed by one or moreprocessors of an exposure apparatus, the program causes the exposureapparatus to perform the operations of FIG. 7. The non-transitorycomputer readable medium includes a hard disk drive, an optical disk, aflash memory, and any other suitable memories.

In step S701, an exposure map is read from a memory. The exposure mapdefines a matrix of exposure areas (an exposure area is one scan area inthe scanner) and includes a size of the exposure area and the numbers ofrows and columns of the exposure areas over a wafer. FIGS. 8A and 8Bshows various exposure maps. FIG. 8A show a 9×6 matrix of the exposureareas, and FIG. 8B show a 7×7 matrix of the exposure areas.

Then, in step S702, a chip area layout is read from the memory. The chiplayout defines matrix of chip areas within one exposure area, andincludes a size of the chip area and the numbers of rows and columns ofthe chip areas within one exposure area. One chip area corresponds toone semiconductor die (chip). FIGS. 9A-9G show various layouts of thechips areas. FIG. 9A shows a 4×6 matrix, FIG. 9B shows a 4×7 matrix,FIG. 9C shows a 3×6 matrix, FIG. 9D shows a 3×4 matrix, FIG. 9E shows a2×4 matrix and FIG. 9F shows a 2×2 matrix. FIG. 9G shows a single chiparea within one exposure area.

In step S703, by using the exposure map and the chip area layout, theboundary between the focus control effective region and the focuscontrol exclusion region similar to FIGS. 6A and 6B is defined. In someembodiments, it is determined whether each exposure area overlaps theperiphery of the effective region of the wafer. Then, for the exposureareas overlapping the periphery of the effective region of the wafer, itis determined whether each chip area overlaps the periphery of theeffective region of the wafer. When the entire chip area is within theperiphery of the effective region of the wafer, the chip area isdetermined as a part of the focus control effective region.

Then, a wafer coated with a photo resist from a “lot” of wafers (e.g.,25 or 50 wafers) is loaded into the optical scanner.

In step S704, focus-leveling measurement over the wafer is performed,and then exposure (scanning) is performed in step S705. In the exposure,the focus-leveling data measured in step S704 is utilized. As set forthabove, when the measuring points are located in the focus controlexclusion region, the measurement data thereof are not used in theexposure step S705 in some embodiments. In other embodiments, when themeasuring points are located in the focus control exclusion region, thefocus-leveling measurement is not performed or measured data is notstored in step S704. In other embodiments, as explained with FIG. 3, thefocus-leveling measurement is performed just before exposing theexposure area.

The wafers are exposed one-by-one until all wafers in the lot areexposed (step S706 to step S704). When the last wafer is exposed (“Y” atstep S706), the next lot of wafers is set to the optical scanner. Whenthe next lot is for the same semiconductor chips having the sameexposure map and the chip area layout (“Y” at step S707), the exposureof the wafer is performed using the previously set focus controleffective region data. When the next lot is for a differentsemiconductor chip having a different exposure map and chip area layout(“N” at step S707), a new exposure map and a new chip area layout areread from a memory, and a new focus control effective region is set.

FIGS. 10A and 10B show one of the advantageous effects of theembodiments of the present disclosure. FIG. 10A shows a rate of thedefocused chip areas according to experimentation in the case where acircular boundary between the focus control effective region and thefocus control exclusion region is set similar to FIGS. 5A and 5B. Thehorizontal axis shows chip area matrix within one exposure area. Thesizes of the chip areas may be different from each other. As shown inFIG. 10A, when many chip areas are arranged in one exposure area, more“bad” chips occur.

FIG. 10B shows a simulated result when the flexible and non-circularboundary between the focus control effective region and the focuscontrol exclusion region is set similar to FIGS. 6A and 6B. Comparedwith FIG. 10A, the number of the “bad” chips can be reduced, which inturn increases the number of “good” chips.

In the foregoing embodiments, an optical scanner is employed. However,the foregoing embodiments can be applied to an optical stepper and anextreme ultra violet (EUV) scanner.

The various embodiments or examples described herein offer severaladvantages over the existing art, as set forth above. It will beunderstood that not all advantages have been necessarily discussedherein, no particular advantage is required for all embodiments orexamples, and other embodiments or examples may offer differentadvantages.

In the present disclosure, by flexibly setting the boundary between thefocus control effective region and the focus control exclusion regiondepending on the exposure map and the chip area layout, it is possiblereduce the number of “bad” chips caused by insufficient focus-levelingcontrol near the edge of the wafer.

In accordance with one aspect of the present disclosure, in a methodexecuted in an exposure apparatus, a focus control effective region anda focus control exclusion region are set based on an exposure map and achip area layout within an exposure area. Focus-leveling data aremeasured over a wafer. A photo resist layer on the wafer is exposed withan exposure light by using the exposure apparatus. A plurality of chipareas are included in the exposure area. When a chip area of theplurality of chip areas is located within an effective region of awafer, the chip area is included in the focus control effective region,and when a part of or all of a chip area of the plurality of chip areasis located on or outside a periphery of the effective region of thewafer, the chip area is included in the focus control exclusion region.In the exposing, a focus-leveling is controlled by using thefocus-leveling data measured at the focus control effective region. Inone or more of the foregoing and following embodiments, thefocus-leveling data measured at the focus control exclusion region arenot used to control the focus-leveling. In one or more of the foregoingand following embodiments, a boundary between the focus controleffective region and the focus control exclusion region is not circular.In one or more of the foregoing and following embodiments, the boundarybetween the focus control effective region and the focus controlexclusion region has multiple corners. In one or more of the foregoingand following embodiments, the multiple corners include 90 degreecorners and 270 degree corners. In one or more of the foregoing andfollowing embodiments, the boundary between the focus control effectiveregion and the focus control exclusion region is set along edges of someof the plurality of chip areas. In one or more of the foregoing andfollowing embodiments, different focus control effective regions andfocus control exclusion regions are set for different exposure maps. Inone or more of the foregoing and following embodiments, differentboundaries between the focus control effective regions and the focuscontrol exclusion regions are set for different chip layouts in theexposure area. In one or more of the foregoing and followingembodiments, the measuring focus-leveling data is not performed for thefocus control exclusion region. In one or more of the foregoing andfollowing embodiments, the exposure apparatus is one of an opticalscanner, an optical stepper and an extreme ultra violet scanner. In oneor more of the foregoing and following embodiments, a boundary betweenthe focus control effective region and the focus control exclusionregion is set within a periphery of the effective region of the wafer,the effective region of the wafer has a circular shape, and a diameterof the effective region of the wafer is 2-15 mm smaller than a diameterof the wafer.

In accordance with another aspect of the present disclosure, in a methodexecuted in an exposure apparatus, a first exposure map and a first chiparea layout within a first exposure area for a first lot of wafers isobtained. A first focus control effective region and a first focuscontrol exclusion region are set based on the first exposure map and thefirst chip area layout. First focus-leveling data are measured over awafer of the first lot. A photo resist layer on the wafer of the firstlot is exposed with an exposure light by using the exposure apparatus.After all wafers in the first lot are exposed, a second exposure map anda second chip area layout within a second exposure area for a second lotof wafers are obtained. A second focus control effective region and asecond focus control exclusion region are set based on the secondexposure map and the second chip area layout. Second focus-leveling dataover a wafer of the second lot are measured. A photo resist layer on thewafer of the second lot is exposed with an exposure light by using theexposure apparatus. The first focus control effective region and thefirst focus control exclusion are different from the second focuscontrol effective region and a second focus control exclusion,respectively. In one or more of the foregoing and following embodiments,in the exposing the photo resist layer on the wafer of the first lot, afocus-leveling is controlled by using the first focus-leveling datameasured at the first focus control effective region, and in theexposing the photo resist layer on the wafer of the second lot, afocus-leveling is controlled by using the second focus-leveling datameasured at the second focus control effective region. In one or more ofthe foregoing and following embodiments, the first focus-leveling datameasured at the first focus control exclusion region are not used tocontrol the focus-leveling in the exposing the photo resist layer on thewafer of the first lot, and the second focus-leveling data measured atthe second focus control exclusion region are not used to control thefocus-leveling in the exposing the photo resist layer on the wafer ofthe second lot. In one or more of the foregoing and followingembodiments, at least one of a first boundary between the first focuscontrol effective region and the first focus control exclusion regionand a second boundary between the second focus control effective regionand the second focus control exclusion region is not circular. In one ormore of the foregoing and following embodiments, at least one of a firstboundary between the first focus control effective region and the firstfocus control exclusion region and a second boundary between the secondfocus control effective region and the second focus control exclusionregion has multiple corners. In one or more of the foregoing andfollowing embodiments, wherein the multiple corners include 90 degreecorners and 270 degree corners. In one or more of the foregoing andfollowing embodiments, a first boundary between the first focus controleffective region and the first focus control exclusion region and asecond boundary between the second focus control effective region andthe second focus control exclusion region are set within a periphery ofthe effective region of the wafer. In one or more of the foregoing andfollowing embodiments, the effective region of the wafer has a circularshape, and a diameter of the effective region of the wafer is 2-15 mmsmaller than a diameter of the wafer.

In accordance with another aspect of the present disclosure, in a methodexecuted in an optical scanner, an exposure map and a chip area layoutwithin an exposure area are obtained. A focus control effective regionand a focus control exclusion region are set based on the exposure mapand the chip area layout. Exposing a photo resist layer on the waferwith an exposure light by using the optical scanner using the set focuscontrol effective region. a plurality of chip areas are included in theexposure area. When a chip area of the plurality of chip areas islocated within an effective region of a wafer, the chip area is includedin the focus control effective region, and when a part of or all of achip area of the plurality of chip areas is located on or outside aperiphery of the effective region of the wafer, the chip area isincluded in the focus control exclusion region. In the exposing, afocus-leveling is controlled at the focus control effective region.

In accordance with another aspect of the present disclosure, an opticalscanner includes a projection lens, a wafer stage on which a wafercoated with a photo resist layer is placed, a focus-leveling sensor fordetecting a height and a tilt of the wafer, a controller for controllingthe wafer stage and the focus-leveling sensor, and a memory. The memoryis configured to store an exposure map set over a wafer set and a chiparea layout within an exposure area. The controller is configured to seta focus control effective region and a focus control exclusion regionbased on the exposure map and the chip area layout. An exposure areacorresponding to one scan is set by the optical scanner. A plurality ofchip areas are included in the exposure area. When a chip area of theplurality of chip areas is located within an effective region of awafer, the chip area is included in the focus control effective region,and when a part of or all of a chip area of the plurality of chip areasis located on or outside a periphery of the effective region of thewafer, the chip area is included in the focus control exclusion region.In the exposing, a focus-leveling is controlled by using thefocus-leveling data measured at the focus control effective region. Inone or more of the foregoing and following embodiments, thefocus-leveling data measured at the focus control exclusion region arenot used. In one or more of the foregoing and following embodiments, aboundary between the focus control effective region and the focuscontrol exclusion region is not circular. In one or more of theforegoing and following embodiments, the boundary between the focuscontrol effective region and the focus control exclusion region hasmultiple corners. In one or more of the foregoing and followingembodiments, the multiple corners include 90 degree corners and 270degree corners. In one or more of the foregoing and followingembodiments, the boundary between the focus control effective region andthe focus control exclusion region is set along edges of some of theplurality of chip areas. In one or more of the foregoing and followingembodiments, different focus control effective regions and focus controlexclusion regions are set for different exposure maps. In one or more ofthe foregoing and following embodiments, different boundaries betweenthe focus control effective regions and the focus control exclusionregions are set for different chip layouts in the exposure area. In oneor more of the foregoing and following embodiments, the measuringfocus-leveling data is not performed for the focus control exclusionregion. In one or more of the foregoing and following embodiments, aboundary between the focus control effective region and the focuscontrol exclusion region is set within a periphery of the effectiveregion of the wafer, the effective region of the wafer has a circularshape, and a diameter of the effective region of the wafer is 2-15 mmsmaller than a diameter of the wafer.

In accordance with another aspect of the present disclosure, a Anexposure apparatus includes a projection lens, a wafer stage on which awafer coated with a photo resist layer is placed, a focus-levelingsensor for detecting a height and a tilt of the wafer, a controller forcontrolling the wafer stage and the focus-leveling sensor, and anon-transitory memory storing a program. When the program is executed byone or more processors of the controller, causes the exposure apparatusto perform: obtaining an exposure map and a chip area layout within anexposure area; setting a focus control effective region and a focuscontrol exclusion region based on the exposure map and the chip arealayout; measuring focus-leveling data over a wafer; and exposing a photoresist layer on the wafer with an exposure light by using the exposureapparatus. A plurality of chip areas are included in the exposure area.When a chip area of the plurality of chip areas is located within aneffective region of a wafer, the chip area is included in the focuscontrol effective region, and when a part of or all of a chip area ofthe plurality of chip areas is located on or outside a periphery of theeffective region of the wafer, the chip area is included in the focuscontrol exclusion region. In the exposing, a focus-leveling iscontrolled by using the focus-leveling data measured at the focuscontrol effective region. In one or more of the foregoing and followingembodiments, the focus-leveling data measured at the focus controlexclusion region are not used. In one or more of the foregoing andfollowing embodiments, a boundary between the focus control effectiveregion and the focus control exclusion region is not circular. In one ormore of the foregoing and following embodiments, the boundary betweenthe focus control effective region and the focus control exclusionregion has multiple corners. In one or more of the foregoing andfollowing embodiments, the boundary between the focus control effectiveregion and the focus control exclusion region is set along edges of someof the plurality of chip areas. In one or more of the foregoing andfollowing embodiments, different focus control effective regions andfocus control exclusion regions are set for different exposure maps. Inone or more of the foregoing and following embodiments, differentboundaries between the focus control effective region and the focuscontrol exclusion region are set for different chip layouts in theexposure area. In one or more of the foregoing and followingembodiments, a boundary between the focus control effective region andthe focus control exclusion region is set within a periphery of theeffective region of the wafer, the effective region of the wafer has acircular shape, and a diameter of the effective region of the wafer is2-15 mm smaller than a diameter of the wafer.

In accordance with another aspect of the present disclosure, an exposureapparatus includes a projection lens, a wafer stage on which a wafercoated with a photo resist layer is placed, a focus-leveling sensor fordetecting a height and a tilt of the wafer, a controller for controllingthe wafer stage and the focus-leveling sensor, and a non-transitorymemory storing a program. When the program is executed by one or moreprocessors of the controller, causes the exposure apparatus to perform:obtaining a first exposure map and a first chip area layout within afirst exposure area for a first lot of wafers; setting a first focuscontrol effective region and a first focus control exclusion regionbased on the first exposure map and the first chip area layout;measuring first focus-leveling data over a wafer of the first lot;exposing a photo resist layer on the wafer of the first lot with anexposure light by using the exposure apparatus; after all wafers in thefirst lot are exposed, obtaining a second exposure map and a second chiparea layout within a second exposure area for a second lot of wafers;setting a second focus control effective region and a second focuscontrol exclusion region based on the second exposure map and the secondchip area layout; measuring second focus-leveling data over a wafer ofthe second lot; and exposing a photo resist layer on the wafer of thesecond lot with an exposure light by using the exposure apparatus. Thefirst focus control effective region and the first focus controlexclusion are different from the second focus control effective regionand a second focus control exclusion, respectively.

In accordance with another aspect of the present disclosure, anon-transitory computer readable medium stores a program. When theprogram is executed by one or more processor of an exposure apparatus,the program causes the exposure apparatus to perform: obtaining anexposure map and a chip area layout within an exposure area. A focuscontrol effective region and a focus control exclusion region are setbased on the exposure map and the chip area layout. Focus-leveling dataare measured over a wafer. A photo resist layer on the wafer is exposedwith an exposure light by using the exposure apparatus. A plurality ofchip areas are included in the exposure area. When a chip area of theplurality of chip areas is located within an effective region of awafer, the chip area is included in the focus control effective region,and when a part of or all of a chip area of the plurality of chip areasis located on or outside a periphery of the effective region of thewafer, the chip area is included in the focus control exclusion region.In the exposing, a focus-leveling is controlled by using thefocus-leveling data measured at the focus control effective region.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A method executed in an exposure apparatus,comprising: obtaining a wafer exposure map, which defines a matrix ofexposure fields per wafer and a matrix of chip areas within one exposurefield; defining, based on the wafer exposure map, valid chip areas whenan entirety of a given chip area is within a first circular perimeter,the valid chip areas including at least one first chip area an entiretyof which is within a second circular perimeter having a smaller diameterthan the first circular perimeter, and at least one second chip areawhich overlaps the second circular perimeter, and defining, based on thewafer exposure map, invalid chip areas each of which overlap the firstcircular perimeter; and exposing one exposure field of the matrix ofexposure field, wherein: the exposing one exposure field comprises:measuring focus-leveling data by using a focus-leveling sensor providinga plurality of laser beams arranged in an X direction, while moving thewafer in a Y direction; and exposing a part of the scanning area by anexposing light having a slit shape extending in the X direction by usingone or more measured focus-leveling data, while moving the wafer in theY direction, and the measured focus-leveling data corresponding to validchip areas are used in the exposing to control focus-leveling, and themeasured focus-leveling data corresponding to the invalid chip areas arenot used in the exposing.
 2. The method of claim 1, wherein the firstcircular perimeter corresponds to an outer perimeter of the wafer. 3.The method of claim 2, wherein the diameter of the second circularperimeter is 2-15 mm smaller than the diameter of the first circularperimeter.
 4. The method of claim 1, wherein the exposing one exposurefield is repeated to exposed all the matrix of the exposure field. 5.The method of claim 1, wherein when an entirety of one exposure field iswithin the second circular perimeter, the chip areas of the one exposurefield are valid chip areas.
 6. The method of claim 1, wherein theexposure light is an extreme ultra violet light.
 7. The method of claim1, wherein the exposure light is a deep ultra violet light.
 8. Anoptical scanner, comprising: a projection lens; a wafer stage on which awafer coated with a photo resist layer is placed; a focus-levelingsensor for detecting a height and a tilt of the wafer; a controller forcontrolling the wafer stage and the focus-leveling sensor, and includinga processor and a memory storing a program; the program, when executedby the processor, causes the controller to perform: obtaining a waferexposure map, which defines a matrix of exposure fields per wafer and amatrix of chip areas within one exposure field; defining, based on thewafer exposure map, valid chip areas when an entirety of a given chiparea is within a first circular perimeter, the valid chip areasincluding at least one first chip area an entirety of which is within asecond circular perimeter having a smaller diameter than the firstcircular perimeter, and at least one second chip area which overlaps thesecond circular perimeter, and defining, based on the wafer exposuremap, invalid chip areas each of which overlap the first circularperimeter; and exposing one exposure field of the matrix of exposurefield, the exposing one exposure field comprises: measuringfocus-leveling data by using the focus-leveling sensor providing aplurality of laser beams arranged in an X direction, while moving thewafer in a Y direction; and exposing a part of the scanning area by anexposing light having a slit shape extending in the X direction by usingone or more measured focus-leveling data, while moving the wafer in theY direction, and the measured focus-leveling data corresponding to validchip areas are used in the exposing to control focus-leveling, and themeasured focus-leveling data corresponding to the invalid chip areas arenot used in the exposing.
 9. The apparatus of claim 8, wherein the firstcircular perimeter corresponds to an outer perimeter of the wafer. 10.The apparatus of claim 9, wherein the diameter of the second circularperimeter is 2-15 mm smaller than the diameter of the first circularperimeter.
 11. The apparatus of claim 8, wherein the exposing oneexposure field is repeated to exposed all the matrix of the exposurefield.
 12. The apparatus of claim 8, wherein when an entirety of oneexposure field is within the second circular perimeter, the chip areasof the one exposure field are valid chip areas.
 13. The apparatus ofclaim 8, wherein the exposure light is an extreme ultra violet light.14. The apparatus of claim 8, wherein the exposure light is a deep ultraviolet light.
 15. A method executed in an exposure apparatus,comprising: obtaining a wafer exposure map, which defines a matrix ofexposure fields per wafer and a matrix of chip areas within one exposurefield; defining a focus control effective region and a focus controlexclusion region, based on the wafer exposure map; exposing one exposurefield of the matrix of exposure field, wherein: a boundary between thefocus control effective region and the focus control exclusion region isacross at least one exposure field, the exposing one exposure fieldcomprises: measuring focus-leveling data by using a focus-levelingsensor providing a plurality of laser beams arranged in an X direction,while moving the wafer in a Y direction; and exposing a part of thescanning area by an exposing light having a slit shape extending in theX direction by using one or more measured focus-leveling data, whilemoving the wafer in the Y direction, and the measured focus-levelingdata corresponding to chip areas within the focus-control effectiveregion are used in the exposing to control focus-leveling, and themeasured focus-leveling data corresponding to chip areas within thefocus-control exclusion region are not used in the exposing.
 16. Themethod of claim 15, wherein the defining the focus control effectiveregion and the focus control exclusion region comprises: defining, basedon the wafer exposure map, valid chip areas when an entirety of a givenchip area is within a first circular perimeter, the valid chip areasincluding at least one first chip area an entirety of which is within asecond circular perimeter having a smaller diameter than the firstcircular perimeter, and at least one second chip area which overlaps thesecond circular perimeter; defining, based on the wafer exposure map,invalid chip areas each of which overlap the first circular perimeter;and determining the focus control effective region to include all validchip areas, and the focus control exclusion region to includes allinvalid chip areas.
 17. The method of claim 16, wherein: the firstcircular perimeter corresponds to an outer perimeter of the wafer, andthe diameter of the second circular perimeter is 2-15 mm smaller thanthe diameter of the first circular perimeter.
 18. The method of claim17, wherein the boundary between the focus control effective region andthe focus control exclusion region is not circular.
 19. The method ofclaim 18, wherein the boundary between the focus control effectiveregion and the focus control exclusion region has multiple corners. 20.The method of claim 16, wherein the exposure light is an extreme ultraviolet light.